The present invention relates generally to methods and apparatus for controlling the flow of gases through compression equipment. More particularly, the present invention relates to methods and apparatus for check valves for compression equipment. Still more particularly, the present invention relates to check valves with rotating closure members.
Reciprocating compressors employ a cyclic process for compressing fluids that involves the suction of low pressure fluid into the compressor, compressing that fluid, and allowing the discharge of pressurized fluid from the compressor. Valves, generally known as check valves, are used to control the suction and discharge of fluids into and out of the compressor.
Many existing suction and discharge valves for the positive displacement compression equipment consist of plates, springs and seats. The operation of this valve is such that the valve plate lifts up from the seat by the gas forces and the spring forces the valve plate to reseat itself. This action causes the valve parts to flex in a fatiguing manner each time the piston cycles. This fatiguing action limits the life of the valve components to a short duration, typically less than a year. As a result, the suction and discharge valves require frequent maintenance, which amounts to very high cost due to product loss and component replacement cost.
In order to extend the useful life of conventional check valves, designers often seek to minimize the flexing of the component parts. In order to minimize the flexing, the valve lifting height is limited, which also limits the area available for the flow of fluids. Because the area available for flow is a limiting factor in the capacity of the pump, reducing this area often leads to designs utilizing multiple valves. Multiple valves not only increase the initial capital cost of the equipment but also increase the cost of maintenance.
The variables used to design conventional valves are numerous and designers historically rely heavily on empirical and experimental data in determining lifting height and opening pressures. Once a conventional check valve system is designed and built, the operation of those valves is limited to the operating parameters originally selected. Therefore, any change the fluid physical properties, thermodynamic properties and operational procedures may negatively affect the performance of the compression equipment and lead to even shorter life for the check valves.
Thus, there remains a need to develop methods and apparatus for controlling flow through compression equipment that overcome some of the foregoing difficulties while providing more advantageous overall results.